Field of the Invention
This invention relates to the general field of rotor vehicles, and more specifically, to an improved design with superior performance and reliability. This invention reduces the overall size and moving parts of prior art rotorcraft, such as helicopters, quadcopters and other manned and unmanned aerial vehicles (UAVs), to achieve superior performance and reliability. The invention, capable of vertical takeoff and landing (VTOL), uses three swashless, variable-pitch vertical lift main rotors with a yaw tail rotor system. The two rear (“aft”) main rotors can be, optionally, tiltrotors, which means they pivot to increase forward speed without the increased coefficient of drag inherent in tilting the entire vehicle. This improves the aerodynamic properties of the fuselage. The three main rotors are positioned in an equilateral triangular configuration, improving balance, increasing load-bearing strength, and making it more compact in size. Movements are controlled through changes in pitch, allowing the motor(s) to maintain constant governed rotations per minute (RPM), maximizing drivetrain efficiency. Vehicle configurations disclosed herein allow for smaller vehicle size with “greater performance” (i.e. more agility, more power, faster response to pilot/flight controller inputs, and a stronger, more rigid, and yet lighter-weight structure) than prior art vehicles.
History of the Invention's Industry
Prior art single rotor and multi-rotor vehicles have dominated the marketplace. Since the Wright Brothers first took flight and Jacques Cousteau explored our oceans, humans have relied on innovative transportation to solve challenging problems. Today, the convergence of technology and transportation is creating new, safer and more efficient modes of transportation. Breakthroughs in autonomous systems are revolutionizing ground-based travel, but innovation around legacy rotorcraft designs, like helicopters, has not been updated.
Along with the overnight popularity, some consider current UAS to have serious problems. One such problem is battery life. Most of the currently popular drone models have a battery life of around twenty minutes. This is problematic as it often takes several minutes just to get the drone airborne and in position to begin its mission. Considering that safe operations usually require at least five minutes of buffer time between when you expect to land and when the battery runs out, this often leaves between ten and fifteen “useful” minutes of operation. Considering the relatively slow horizontal speed of many drones on the market today, this severely limits the distance a drone can be flown to accomplish a mission. Some of the short battery life is due to the batteries themselves, but other reasons include that fact that most drones today are not engineered very efficiently.
Another issue faced by people and groups ranging from hobbyists to search and rescue personnel is that most “drones” work only in the air, while most “submersibles” work only in the water. Thus, it would be desirable to have a single unmanned system that could both fly in the air and move underwater.
Thus there has existed a long-felt need for a vehicle that can avoid all of the aforementioned problems. The current invention provides just such a solution by having an improved vehicle with three “vertical” propellers for which the pitch can be adjusted, but which can operate at full or nearly full capacity throughout the flight. By not controlling the elevation and direction/location of the drone by changing the speed at which various propellers spin, the invention provides a more efficient operation, which not coincidentally helps to give the operator a longer battery life. The invention also has a fail-safe automatic disengage system that disengages the propellers from the power plant in case of engine failure. This allows the unit to auto-rotate, similar to the auto-rotation that a helicopter undergoes when it loses power. The vehicle also has a variable pitch yaw system that provides superior control to the prior art which teaches the use of the four propellers to control yaw.
Market Potential
Aerial transportation does not share the infrastructure requirements of ground-based transportation solutions. This is particularly valuable in high population density areas where traffic congestion increases costs and limits the efficiency of prior art transportation. The utility of efficient aerial vehicles capable of three-dimensional travel and VTOL will revolutionize the transportation of goods and people.
Challenges
Unmanned Aerial Systems (UAS) have introduced a wave of new technology. UAS have demonstrated potential in reducing costs and risks with driverless solutions, but cannot compete with the utility of traditional rotorcraft. UAS, traditional rotorcraft and other prior art solutions have inherent safety and reliability limitations in their fundamental designs, which prevent usability in industries such as transportation with high safety and reliability requirements. An increase in hardware and software complexity has arisen to compensate for these shortcomings. This invention remedies these deficiencies with a completely novel design that meets the safety and reliability standards of human transportation by integrating technology from both traditional rotorcraft and state-of-the-art UAS.
Unique Vehicle Configuration
This invention has identified an ideal vehicle configuration with fixed geometric relationships (see FIG. 2), allowing for a scalable design that integrates the best aspects of prior art designs into one vehicle and can accommodate a variety of use cases through customization with modular components. The superior performance of the vehicle is a direct result of the marriage of the following features:                Active Main Tri-Rotor Systems        Stability        Form Factor (size)        Swashless Variable Pitch Rotor Management System        Autorotation        Tiltrotors        Active and Independent Yaw Tail Rotor System        Redundant system        Modular Design        Fuselage        Payload Capacity        Monocoque        Amphibious        
Equilateral Triangular Rotor Configuration
The vehicles according to the current disclosure use a tri-rotor design, the minimum number of rotors required to achieve maneuverability through variable pitch, the most efficient system for rotorcraft control. The use of three smaller main rotor heads, as opposed to one large helicopter rotor head, creates the same lift with the same surface area but reduced size and mass, improving stability and efficiency. The equilateral triangular orientation of the main rotors keeps the relationships in vehicle dynamics fixed around the center axis during maneuvers, providing maximum stability. Spinning smaller rotor blades compared to a single rotor vehicle with the same rotor blade surface area allows the vehicle to achieve higher rpm due to lower rotational mass at the rotorhead. This creates more relative lift per unit of rotor blade surface area and greater stability without increasing torque, minimizing the requirement for torque management from the yaw tail system. The use of different rotor blade designs like semi-symmetrical blades further improves the efficiency and lift capabilities as rpm increases.
Independent Main Rotor Systems
The aerial environment of a vehicle is in a constant state of change, requiring a vehicle capable of adapting to constant change in order to perform even the simplest tasks, like holding position. This vehicle uses independent rotor systems for each of the three main rotors to address disparities in the flight conditions for each individual rotor. Allowing each rotor to act independently improves the performance. This vehicle is the only one to combine a multirotor vehicle with variable pitch, independent and active rotor systems, and the safety benefits of autorotation.
Active Main Rotor Systems
Building on the ability of each main rotor drive system to act independently is the ability to actively adjust each rotor system to cope with highly dynamic environments and the performance-sapping hazards of retreating blade stall. The more extreme the operating conditions (wind speed, precipitation, etc.) and the higher the speed of an aircraft maneuver, the greater the differential between leading and trailing rotor blades within each rotor and also the differential between each rotor in the trirotor configuration, causing a vehicle without an active ability to adapt to stall and lose control. Actively regulating the performance characteristics of each rotor prevents the vehicle from losing performance in operating environments that would disrupt the stability, balance and efficiency of prior art rotorcraft without active systems. In the event that a main drive rotor becomes obstructed, the vehicle's active and independent drive systems will utilize the remaining drive rotors to perform an emergency landing by yawing the aircraft around its central axis and balancing the vehicle in a constant circular rotation.
Stability
Helicopters and rotary UAVs both have VTOL capability, but designs are limited by retreating blade stall. Retreating blade stall results from the disparity between leading and trailing blades in a rotor. The leading blade spins into the direction of oncoming airflow generating lift and positive velocity, but the trailing blade spins in the opposite direction of airflow generating less lift and negative velocity, or drag. The faster the speed of flight, the higher the possibility that this disparity in lift caused by retreating blade stall will upset the stability of the vehicle. This invention primarily eliminates retreating blade stall by using an equilateral triangular rotor configuration along with independent and active rotor systems to distribute and balance the effects of drag across the vehicle's three rotors to negate the adverse effects of retreating blade stall.
Form Factor
This tri-rotor configuration has smaller packaging and requires less components than a single rotor, with a minimal multi-rotor setup, it is the most efficient configuration for a rotorcraft of the same size.
Variable Pitch
Variable pitch is the key to the superior performance of our vehicle design. Lift is controlled through a variable pitch system, meaning the motors run at a fixed optimal rpm, able to adjust pitch to execute maneuvers with faster responses to the pilot's inputs (“low-latency”) compared to prior art systems. This eliminates more moving parts compared to prior art, further increasing reliability and efficiency, in addition to increasing reaction times, precision and control. It is possible to further improve the benefits of variable pitch design by reducing pitch on trailing blades through new rotor head designs to eliminate drag using low-latency magnetic actuators to adjust the pitch of individual blades as they are rotated. The minimal latency of a variable pitch system maximizes the performance of any avionics installed on the vehicle.
Swashless Rotor System
This invention removes the complexity of conventional helicopter main rotor systems, by removing the swashplate system and significantly reducing the number of moving parts. The equilateral triangular rotor system effectively acts as a larger and more robust swashplate, replacing the need for a swashplate on the rotor shaft. This allows for a shorter rotor shaft, reducing the pendulum effect that results in instability, wear and packaging inefficiency of longer rotor shafts of prior art rotor vehicles. Removal of the swashplate reduces latency in reaction times because the mechanical responses are direct and do not have to pass through an additional swashplate component. In addition to saving weight, the elimination of unnecessary moving parts reduces the lag, wear and inefficiency of the entire system, while streamlining the drivetrain to be more reliable and compact.
Autorotation
Engines, batteries and other power sources can fail, but prior art designs, with the exception of helicopters, often have no provisional safety features to allow safe landing without a power source. In traditional UAS, when the battery fails, the vehicle normally just drops out of the sky, potentially endangering any people or property that happens to be underneath. This danger has been the driving force behind governing bodies like the FAA's support of restrictions over populated airspace. Fixed wing designs can land without a power source, but require runways, which are not always available in an emergency. Autorotation on all 3 rotors, means that our vehicle can land itself safely in the unlikely event of a drivetrain failure. Autorotation uses ambient air pressure and the force of gravity to rotate the blades, providing enough lift to avoid the vehicle from falling out of the sky. Instead it allows for a controlled landing, even without an active drivetrain. The one-way hub system works like a freewheel, allowing the rotors to spin freely when the motor(s) are disengaged. The force exerted by gravity on the vehicle is enough to force airflow around the rotor blades, causing them to spin and generate sufficient lift to safely land the vehicle. This mechanical redundancy eliminates the need for backup systems and reserve powertrains, further reducing the required weight and complexity of the vehicle, in order to safely land in case of an emergency. Mechanical redundancy is instantaneous and minimizes reliability and latency issues should adverse events occur and require an emergency landing.
Tiltrotors
Aerial vehicles have always been challenged by the conflicting tasks of takeoff and flight. Vertical takeoff is the most desirable form of takeoff because it requires minimal space and provides maximum control over stops and turns, but, once in flight, it is forward thrust that is required. With traditional UAS, an exclusive choice must be made between vertical or horizontal design efficiency. This is an inherently inefficient situation. In this invention, the two main aft rotors of the main rotor configuration are tiltrotors, capable of articulating into a forward position when in forward flight to optimize thrust. When combined with the aerodynamics of the monocoque, this forward motion generates additional lift and increases the efficiency and performance envelope of the vehicle.
Yaw Tail
The use of a yaw tail in this invention allows the vehicle to maintain directional stability under extreme environmental conditions and maneuvers, as well as improving precision and agility. Lack of directional control causes prior art designs to become increasingly unstable in adverse conditions and advanced maneuvers. The independent and active yaw control system combines the best features of prior art designs to maximize the benefits of this vehicle's configuration. Non-independent prior art designs with limited yaw control are primarily focused on counteracting engine torque, an inefficient use of vehicle's energy which adversely impacts main rotor performance as well.
Torque Management
Prior art fixed pitch multirotor UAS rely on changing opposing motor RPM to counter torque and manage yaw, while variable pitch multirotor UAS rely on changing pitch of opposing rotors to counteract torque and manage yaw. This approach to achieving yaw control is inefficient and destabilizes the vehicle. Single rotor helicopters spin their blades in one direction, requiring a yaw tail rotor to cancel this twisting force, or torque, that would otherwise destabilize the vehicle. A three rotor setup also requires an active yaw system, but is even more efficient because the aft main rotors spin in opposing directions, cancelling each other out. This means that the yaw control in our tri-rotor configuration only has to cancel the torque of the front main rotor since the aft main rotors spin in opposite direction, which is smaller and requires less energy compared to a single rotor with greater blade surface area, while maintaining directional stability and efficiency during maneuvers.
Independent Yaw System
This invention improves performance and efficiency, reducing the loss of control through the use of a separate electric motor to drive the independent yaw control system in the tail. Instead of counteracting main drive torque, this design maintains full control in all conditions and maneuvers through the use of an independent and active system. Also, by directly driving the tail rotors, many parts are eliminated currently used in conventional helicopters, (i.e. torque tube, gears, u-joints, gearbox) which are common wear items and failure points.
Active Yaw System
Similar to the independent and active systems on the main rotors, using an active yaw system further improves efficiency and performance in adverse conditions. Because the tail rotor's active yaw system is independent from the main rotors' drivetrain, it does not steal power from or compete with other systems inside the vehicle. Instead, because there is no mechanical linkage to the main rotors, the active yaw can turn itself off completely or change rpm and pitch to counteract undesired forces. The limits of the yaw system are determined by the rotorhead configuration, which can be modified to meet customer needs in our modular design. It also maintains steering control should a failure occur in the main rotor system, resulting in an autorotation landing.
Redundant Systems
Backup systems for mechanical components are integrated into the design to significantly reduce the risk of catastrophic failure to. These redundant systems can apply to any aspect of the vehicle and be mechanical, magnetic, electronic, hydraulic, physical and software-based. One example of such innovations on the vehicle is the redundant dual servo system for the yaw tail rotor and the main tri-rotor systems.
Modular Design
Particular embodiments provide for the central section of the vehicle being a modular fuselage. Because this fuselage houses all of the interchangeable electronics and components, this modular central section can be switched to accommodate different setups for specific industries or applications. In addition to the swappable electronics, this swappable section can be used to change the vehicle power source and allow for other custom modifications based around the same universal platform. In larger models, this detachable central compartment can include a passenger compartment, along with all the required components and safety equipment to transport live cargo. The three identical rotor arms and interchangeable rotors also allow for modular customization to a variety of use case specifications, including future innovations in fan-bladed rotor systems. Similarly, the yaw configuration can be customized to accommodate a variety of single rotor and multirotor specifications. Because this vehicle does not require any electronics as part of its basic configuration, it is an open platform that is compatible with any electronics or avionics solutions.
Fuselage
The vehicle fuselage is a modular weight bearing structure. In addition to housing all of the vehicle components, the fuselage creates the common linkage for all of the vehicles modular components and directs weight towards the center of gravity. The fuselage can be sealed to become watertight, or even padded to produce a secure Faraday Cage. Adaptations of the fuselage will allow for a variety of loadbearing and non-loadbearing applications.
Payload Capacity
Employing a weight bearing structure as the fuselage harnesses the vehicle's payload capacity to add new levels of utility and potential applications for this vehicle design. Helicopters were designed to carry loads inside of their passenger compartment, although some have been adapted to allow for external loads. Prior art UAS have not been designed to carry payloads competing with helicopters. This invention was built from the ground up, utilizing a weight bearing fuselage to support the suspension of heavier external loads relative to prior art designs.
Monocoque
In place of a fuselage, the vehicle can utilize an aerodynamic monocoque. The monocoque minimizes energy consumption when in motion by generating aerodynamic lift when in flight, or underwater. The monocoque also reduces the overall weight of the vehicle and channels airflow over the heatsinks of heat sensitive components to maximize thermodynamic performance when in motion. The monocoque is also designed to simultaneously accommodate internal components and create the padded vehicle legs that allow the vehicle to land safely in the event of an emergency landing over water or solid ground.
Amphibious
Due to the nature of fluid dynamics, aspects of the current disclosure are identical for submersible vehicles. The vehicle can be sealed with a superhydrophobic nanocoating, or other treatment, and allows for the optional addition of ballast tanks to provide submersible operation. Even without the optional ballast tanks, the vehicle can float on the surface of water in the event of an emergency landing or maritime operation.
Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future. Furthermore, the use of plurals can also refer to the singular, including without limitation when a term refers to one or more of a particular item; likewise, the use of a singular term can also include the plural, unless the context dictates otherwise.
The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.